Figure 5.

Mitotic TFIIH is deficient in CTD kinase activity. (a) CTD kinase activity of TFIIH directly purified from mitotic and interphase cells (in vivo, lanes 3,4). The kinase activity of conventionally purified TFIIH is shown in lane 1. Purified TFIIH was pretreated with mitotic or interphase extracts in the presence of ATP (in vitro, lanes 6–7, see diagram at right). (b) Western blot analysis of TFIIH subunits (p62 and CDK7) from samples analyzed in a. This blot shows that similar amounts of TFIIH were used in the assay performed in a. The electrophoretic mobility of CDK7 caused by phosphorylation in mitosis is not resolved in this analysis. The samples were separated on a Bio-Rad mini-gel.